When a patient is administered by intravenous injection, an infusion bottle filled with nutritive liquid or additive is dripped into the patient's body through a tube. It should always be watched by a nurse or patient's family to prevent the exhausting of liquid in the bottle. Such a monitoring job may sometimes be neglected especially, when it is at mid night, by a nurse who may be very sleepy or tired. By applying a photo-electric sensor for monitoring the liquid level in the infusion bottle, it requires higher cost and expense for installing such an electronic system. By applying other detecting methods such as by putting a float sensor in the infusion bottle, the additional detecting articles may cause contamination or infection into the infusion system, hazardous to patient's health.
It is therefore expected to invent an alarm for warning an exhausting infusion bottle, which alarm is simply constructed and easily operated.